Granulocytic ehrlichiosis occurs in mammals such as humans, horses, dogs and cats and is caused by infection of granulocytic cells with the tick-borne agent Anaplasma phagocytophilum (formerly known as Ehrlichia equi). Frequently reported symptoms of granulocytic ehrlichiosis in humans are leukopenia and thrombocytopenia. Common clinical signs in dogs and horses are fever and anexoria.
Indirect immunofluorescence assays (IFA) and enzyme-linked immunosorbent assays (ELISA) are frequently used as aids in the diagnosis of diseases caused by A. phagocytophilum by measuring the binding of antibody from a patient's blood or serum to infected cells, cell lysates or purified ehrlichial proteins. However, these assays are severely limited in usefulness because of sensitivity and specificity issues directly related to the impure nature of the antigen used in these tests. Highly purified reagents are needed to construct more accurate assays. This invention discloses specific synthetic peptide sequences derived from A. phagocytophilum that can be used in place of partially purified proteins, infected cells or cell lysates.